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(No Model.)

L. O. THATGH ER. STEAM GENERATOR. No. 392,579. Patentqd Nov. 6.1.888

N. P'ETERS. Pnm mos a en Wanhingtnn, DC.

Unire LEW IS C. THATCHER, OF CHICAGO, ILLINOIS.

.STEAIVFGENERATOR.

EEPECIFICATION' forming part of Letters Patent No. 392,579, dated November 6,1888.

Application filed July 11,1888.

To all whom it may concern:

Be it known that I, Lnwrs O. TIIATOIIER, a citizen of the United States, and residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Steam-Generators, which is fully set forth in the following specification,

' reference being had to the accompanying drawing, in which the figure represents an elevation, partly in section, of a construction embodying my invention, portions of the boiler proper being broken away to show the con strnction.

My invention relates to steam-boilers, and has for its object to produce an apparatus of this description whereby great economy of fuel may be obtained by utilizing all the heat obtained from the combustion of the same.

To this end my invention consists in certain novel features, which I will now proceed to describe, and will then particularly point'out in the claims.

In the drawing, A represents an outer or inelosiug shell or casing, which is preferably cylindrical in form and constructed of brick-work or other suitable material.

B represents the fire-space or furnace proper, b the grate, and C the ash-pit, these parts occupying the lower portion of the space inclosed by the casing A. At its upper end the casing A terminates in a smoke-stack, D, by means of 1 which the products of combustion are carried ott.

E represents the boiler proper, which occupies the space within the casing A above the fire-space or furnace B. This boiler consists ofa central cylindrical body portion, E, around which are formed one or more spirals, E. In the present instance I have shown two of these spirals, although it is obvious that the number may be varied as desired. Each spiral consists of two plates or series of plates bent into proper form and having their outer edges riveted together, as shown ate. From their outer edges these plates diverge inwardly, their inner edges being flanged up and down, respectively, and connected to the correspondingly-flanged edges of the plates of the other spiral, as shown at e. The outer edges of the spirals are in contact with the inner wall of the Serial No. 279,635. (No model.)

casing A throughout their length, and there are thus formed spiral flues at, extending from the furnace along the entirelength of the boiler and terminating at the top thereof. The body portion E of the boiler is formed, except as to its ends, entirely by the inner flanges of the plates which form the spirals, the ends of said body portion being formed of separate pieces, as shown. At its lower end the boiler is provided with a transverse mud-drum, F, of any usual construction.

In order to support the boiler E within the casing A, I provide at the top of the said casing a spider, G, consisting of a central hub, g, and radial arms 9, these arms resting upon the top of the casing A. Stay-rods H, extending the length of the boiler and suitably secured to the same, extend upward through the hub g of the spider G, their upper ends being threaded to receive nuts h, by means of which they serve to support the boiler.

I represents the steam -pipe, by means of which the steam is drawn from the boiler, and J (shown in dotted lines) represents the feedpipe, by means of which water is supplied to the boiler.

The operation is as follows: The heated gases and other products of combustion pass upward from the furnace B through the spiral flues a, and the water contained in the boiler is thoroughly exposed to their action, since a very large heating-surface is thus obtained, which serves to thoroughly utilize all the heat. Vhen the gases escape at the top of the boiler, practically all the useful heat has been extracted therefrom. By reason of this construction I obtain a greatly increased efficiency of the boiler, and the proportion of water evaporated to the fuel consumed is very great,

It is obvious that various modifications in the details of construction may be made without departing from the principle of my invention, and I therefore do not wish to be understood as limiting myself strictly to the precise details hereinbefore described, andshown in the drawing.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. The combination, with the outer casing,

of the boiler inelosed therein and composed of inner edges flanged, respectively, upward and [0 one or more spirals having their edges in condownward and secured to the corresponding tact with the said casing and forming in conedges of the other spiral, substantially as and junction therewith spiral fiues, substantially for the purposes specified.

as and for the purposes specified.

5 2. The eombinatiomwith the cylindrical con- LEWIS THAFCHER' tral portion, E, of the spirals E, each' eom- Witnesses: posed of two plates or series of plates secured F. MOKEEBY, together at their outer edges and having their B. L. MILES. 

